The present disclosure relates to a solid-state imaging apparatus, a method of manufacturing the same, and an electronic apparatus and more particularly to a solid-state imaging apparatus, a method of manufacturing the same, and an electronic apparatus that can improve the charge transfer efficiency.
A charge coupled device (CCD) solid-state imaging apparatus includes a vertical CCD and a horizontal CCD that are transfer channels for transferring charges collected by a photodiode to an output amplifier.
A vertical transfer register constituted of the vertical CCD transfers charges in a vertical direction when a clock voltage is applied to a gate electrode provided in an upper portion thereof.
Regarding a method of forming the vertical transfer register, there are a surficial channel and a buried channel. The surficial channel has a problem in that, due to Si defects in the surface, electrons are easily captured or electrons not associated with signals are easily generated, which deteriorates the transfer efficiency. Therefore, in general, the buried channel is often employed in the CCD solid-state imaging apparatus. With the buried channel, the channel is formed slightly deep under the surface to transfer electrons.
A method of forming the buried channel will be simply described. First, only areas in which vertical transfer registers are to be formed are opened with a resist mask and N-type ions such as As (arsenic) are implanted, such that N-type transfer channels are formed. Next, an N-type ion implantation using As or the like is further performed on partial areas of the formed N-type transfer channels, such that potential steps in which the potential is set deeper is formed. This potential steps have an effect of assisting in transferring charges.
The potential step is formed by opening only a desired area with a resist mask and performing an ion implantation as described above. Thus, the potential sharply changes at a boundary between the area subjected to the ion implantation and the area not subjected to the ion implantation. Due to such a sharp change in potential, there is a fear that some charges remain when charges are transferred in the vertical direction. The remaining charges directly lead to the deterioration of imager characteristics, which is unfavorable. In view of this, various techniques for improving the charge transfer efficiency have been proposed (e.g., see Japanese Patent Application Laid-open No. 2011-249690, Japanese Patent Application Laid-open No. HEI 08-288492, Japanese Patent Application Laid-open No. HEI 03-285335, and Japanese Patent Application Laid-open No. HEI 08-139304).